This invention relates to a tool assembly which comprises a tool holder and a tool head and wherein the tool head is releasably tightenable to the tool holder by means of clamping elements movable in an opening of the tool head. The clamping elements may be actuated by means of a locking bar which is slidably displaceable in the tool holder.
Tool assemblies of the above-outlined type serve for a rapid replacement or for a rapid change of the angular position of a tool head.
U.S. Pat. No. 4,406,195 issued Sept. 27, 1983 discloses a tool assembly in which, for clamping the tool head against the tool holder, a screw conically tapering towards its end is pressed against the conical outer face of a piston connected to a locking bar. Between the two conical surfaces only a linear contact occurs. Due to the required high clamping forces for the clamping bar thus either a significant wear has to be expected or expensive, wear-resistant materials have to be used. Because of the one-sided engagement of the screw with the conical surface of the piston, a torque is exerted on the components which may lead to a misalignment of these components and thus to an increased friction therebetween.
It is further known to equip the locking bar with a locking (clamping) piston which is connected with a pull rod by means of a wedge (camming) face. The pull rod, while rotation about its own axis is prevented, is moved by a non-shifting body with the intermediary of a thread pair. In such an arrangement the rotary body is exposed to significant axial frictional forces and further, frictional forces are also generated by a misalignment of the clamping piston and the pull rod.